How to create alpha / height maps in Blender for use in e. g. Substance Painter?
I finally found a good, working and as it turns out easy solution to this problem. Credits go to Petr Utinek, he made a tutorial video here.

The steps (I modified them a bit):


Create a mesh, e. g. a gear and switch to Top Ortho view





Select the camera, hit space, search "Align Camera to View" and apply it
Select Render tab, change resolution to 2048x2048 and 100%





Select Data, Orthographic and adjust the Orhtographic Scale





Select the Mesh and assign a Material to it
Select Node Editor, Compositing and Use Nodes
Add a Normalize Node and an Invert Node and link the nodes like this:





add a Plane below the Mesh





Render the scene and save the image





Or to follow the initial question: Easy to re-use by simply e. g. deleting the gear and replacing it with a cylinder




which will result in this